Integrated circuits are designed to operate under a variety of environmental conditions. For example, integrated circuits are designed to operate over a range of temperatures. To ensure that an integrated circuit operates correctly over a particular range of temperatures, the integrated circuit is coupled to a test unit for testing at different temperatures within the particular range. The test unit typically includes a thermal unit that facilitates thermal cooling and control for testing.
However, multi-chip electronic packages (MCPs) create a challenge of testing using conventional thermal units. An MCP includes multiple die, which may comprise logic die, memory die, platform control hub (PCH), and/or digital die, attached or assembled on a substrate. FIGS. 1A and 1B illustrate a top view and a side view, respectively, of one embodiment of a three die MCP.
The problem with testing MCPs using conventional thermal units is an inability to simultaneously establish good mechanical and thermal contacts with each die due to a difference of die heights, a variation in height difference between each die, and warping of electronic packages. FIGS. 2A and 2B illustrate conventional thermal unit configurations for MCPs.
As shown in FIG. 2A, a rotating gimballing mechanism is included to accommodate die height difference. Nevertheless, the existing gimballing mechanism does not provide for sufficient contact across the entire die surfaces, which results in poor thermal cooling and control. FIG. 2B illustrates a three-die MCP in which an offset between the thermal unit and the nominal die height of two of the die creates an area of poor or non-contact.
FIG. 3 illustrates a conventional coil spring mechanism implemented to eliminate the height offset. However, as shown in FIG. 3 this mechanism, as well as the gimballing mechanism, requires large thermal unit profiles to eliminate the height offset.
An additional problem with testing MCPs using conventional thermal units is that inadequate contact coverage between the thermal unit pedestal and die may lead to over stressing and overheating of the die. Even when an interface material is applied, the die-pedestal gap may be large enough to drive over heating.
Currently, in order to compensate for inadequate die-pedestal contact coverage, the test program is changed (e.g., reducing the test power and extending the test time) in order to eliminate die damaged at test. These test program adjustments are undesirable because they often lead to longer test times.